It is already known to care for fractures of femurs or thigh-bones by enlarging in diameter the marrow space by means of a boring fraise and subsequently driving a bone-nail into the marrow space having been enlarged in diameter. When nailing bones in usual manner, the diameter of the marrow space having been enlarged by fraising is greater for approximately 0.5 mm than the outer diameter of the bone-nail for the purpose of preventing jamming of the nail when driving same into the marrow space.
For effecting bone nailing with nails introduced into the marrow space, bone-nails have already been proposed, which consist of a straight tube having a cross section of the shape of a clover-leaf and being provided over the whole length with a longitudinal slot. It has further been proposed to slightly bend these nails for better adapting same to the curvature of the femur. It is also known to provide at the proximal end of the nails a head for applying a driving tool and having, for example, the shape of a cone provided with an internal thread. Known bone-nails have a tip at their distal end for facilitating insertion of the nails into the marrow space.
The longitudinal slot, which can be located either on the convex side or on the concave side of a bone-nail, allows a bone-nail made of a material showing a certain elasticity to reduce its diameter when being driven into the marrow space so that the bone-nail can engage the wall of the marrow space under tension.
It is also known to provide holes at the distal and at the proximal portions of bone-nails for marrow nailing and to insert bolts into these holes after having the nail driven into the marrow space, for anchoring the nail ends within the bone. Thus, the position of the nail is fixed on both sides of the fractured area and it is made sure that the bone does not become shortened after loading the bone immediately after the nailing operation, and this also in case of a fragmentation fracture. Insertion of the bolts is in this case effected by means of a sighting or aiming instrument determining the aligned position of the diametrically opposed holes and a guide means.
It is a drawback of known bone-nails that difficulties frequently arise when driving such nails into the widened marrow space in case the diameter of this marrow space corresponds to the nail diameter or is only slightly greater. When widening the marrow space by fraising, no smooth wall is formed but elevations result which represent an obstacle for sliding the bone-nail into the marrow space. Substantial difficulties can arise particularly if the distal and tipped edge portion of the nail becomes jammed during the driving operation. If, however, the marrow channel is widened by fraising to a diameter substantially exceeding the outer diameter of the nail, the bone is no more unobjectionally fixed in position at the location of fracture.
A further drawback of known bone nails must be seen in the fact that for nailing a right femur or thigh-bone not the same nail can be used as for nailing the left femur or thigh-bone. The reason therefor is that the bolt fixing the nail at the area of inserting this nail at the hip joint can for anatomic reasons not be arranged in normal direction to the longitudinal direction of the nail at this area but must be obliquely arranged, so that the position of the holes accommodating these mentioned bolts and located at the proximal edge portion of the nail is different with a nail for a right femur or thigh-bone and with a nail for a left femur or thigh-bone.
Finally, the known bone nails suffer from the disadvantage that application of the bolts within the area located distant from the hip becomes difficult on account of the nail becoming always rotated around its axis or twisted. For anatomic reasons, the axis of the bolt must, however, extend in normal direction to the plane comprising the curvature of the nail, the bolt being applied from the outside of the condyle of the femur or thigh-bone. In front of and behind this location there are bulky muscles through which the bolt can not be introduced and furthermore the upper knee-joint bag is located at the front side and extends relatively far in upward direction. If the nail becomes now twisted during driving operation on account of the shape of the femur or thigh-bone and in view of its elasticity, the holes originally arranged laterally with their axes substantially in normal position relative to the plane of curvature of the nails are located either in front of or behind that position at which the bolts must be arranged for anatomic reasons for not penetrating either the upper knee-joint bag or the bulky muscles.
It is an object of the present invention to avoid the drawbacks of the known bone-nails.
It is further an object of the invention that the nail can, on the one hand, be easily introduced by a driving operation and, on the other hand, reliably maintain the area of fracture in a fixed position. The nail shall easily find its path with its distal edge portion when being driven into the bone and shall smooth any roughness and any elevations within the marrow space but shall with its middle portion tightly and resiliently engage the wall of the marrow space for achieving a reliable fixation in position of the fractured area. It is a further object of the invention to provide a bone-nail which can be used for right-hand bones as well as for left-hand bones. It is also an object of the present invention to provide a bone-nail with which the driving force exerted on the head of the nail as well as any rotational force exerted on the head of the nail is uniformly distributed or transmitted onto the nail. It is a further object of the invention to design the bone-nail such that also in case of an unintended and undesired rotation of the nail during the driving operation a fixing bolt serving the purpose of anchoring the nail within the bone assumes a position normally extending relative to the plane of curvature of the nail, so that neither the knee-joint bag nor bulky muscles represent an obstacle for inserting the fixing bolt. Finally, it is an object of the invention to design the nail such that threaded bolts can be used as the fixing bolts at the proximal end portion.